SYNTHESIS OF OSMIUM MESO-TETRA-PARA-TOLYLPORPHYRIN CARBENE COMPLEXES (TTP)OS=CRR' (R, R'=PARA-TOLYL R=H, R'=SIME3, CO2ET) - STEREOSELECTIVE, CATALYTIC PRODUCTION OF OLEFINS FROM SUBSTITUTED DIAZOMETHANES

A series of osmium meso-tetra-p-tolylporphyrin carbene complexes, (TTP)Os=CRR' [R,R' = p-tolyl (1); R = H, R' = SiMe3 (2), CO2Et (3)], have been prepared by treating [Os(TTP)]2 with the appropriate diazoalkane (N2CRR'). The carbene complexes, 1-3, and the osmium complexes [Os(TTP)]2, Os(TTP)(CO)(py), and Os(TTP)(py)2 catalytically convert ethyl diazoacetate to diethyl maleate and diethyl fumarate in high yields and high stereoselectivity. The Z/E ratios range from 18:1 to 26:1. Olefin also can be produced from N2C(p-C6H4-CH3)2 but not from N2CHSiMe3.